Metal sheets or coils are typically surface treated with a coating composition prior to being used in subsequent manufacturing processes, for example, in the manufacture of cans or other similar containers. The coating composition acts as a lubricant thereby facilitating handling of the metal sheets or coils. The coating composition also prevents abrasion and scratching and inhibits corrosion which may occur during storage and transport of the metal sheets or coils.
Various coating compositions have been proposed for use as lubricants, for example, naturally occurring vegetable oils and synthetic esters of carboxylic acids. Lubricating oils based on citric acid esters have also been used. EP 0,200,001 describes a lubricating oil containing a citric acid ester and a reaction product of a C.sub.3 to C.sub.18 carboxylic acid and an amine. The resultant lubricating oil is alleged to have improved anti-corrosive properties.
However, in order for a coating composition to be used on an industrial scale it should, ideally, possess a unique combination of properties. If any one property of the combination is missing, then the coating composition is not entirely satisfactory. The compositions used or proposed previously have, for this reason, not been entirely satisfactory.